1. Field of the Invention
This invention relates in general to hand-held tools and in particular to a lockbolt installation tool fitted with a cantilevered support for reacting gravity and installation forces against an operator's forearm and for maintaining a healthful wrist posture.
2. Description of Prior Developments
Lockbolt installation tools are designed to connect or swage lockbolt fasteners on a pair of workpieces being secured together. Typically, the workpieces take the form of two metal sheets or a sheet and frame member in an aircraft structure. Each lockbolt fastener includes a lockbolt having a grooved shank extending through aligned holes in the workpieces. A swageable collar is positioned on a projecting portion of the lockbolt shank.
The lockbolt installation tool commonly includes a fluid-actuated piston-cylinder mechanism and an associated anvil-jaw assembly. The anvil is connected to the fluid cylinder, and the piston is connected to the jaw structure so that axial movement of the piston relative to the cylinder produces a corresponding relative movement of the jaw structure and anvil.
The jaw structure is grippingly connected to the projecting portion of the lockbolt shank, and the anvil is located in axial alignment with the collar. Axial motion of the piston within the fluid cylinder causes the jaw structure to exert a pulling force on the lockbolt and causes the anvil to exert an axial swaging force on the associated collar. The swaging action on the collar causes the collar material to be driven into the grooves in the lockbolt shank, thereby locking the lockbolt-collar assembly to the facially-engaged workpieces.
In many instances, the lockbolt installation tool is a hand-held manually-operated structure having a pistol-grip handle for manipulating and positioning the tool in operative engagement with the lockbolt fastener and collar. Usually the pistol-type handle has a depressible trigger for controlling the application of fluid pressure to the tool cylinder. When manual finger pressure is applied to the trigger, pressurized fluid is introduced into the tool cylinder thereby producing a rapid movement of the piston and a correspondingly rapid swaging of the fastener collar into the lockbolt grooves.
The lockbolt is usually designed with a breakneck groove therein so that during the collar swaging process the relatively high axial force on the lockbolt causes the protruding portion of the lockbolt to be severed from the lockbolt-collar assembly. The severing action takes place at the breakneck groove. The severed portion of the lockbolt, commonly referred to as the pintail, is forcibly ejected away from the lockbolt-collar assembly due to the pulling action of the tool jaws on the protruding portion, or pintail, of the lockbolt.
The lockbolt installation tool usually weighs several pounds. In some cases, the tool can weigh as much as 25 pounds or more. The weight of the tool can stress the worker's hand and wrist, especially after the tool has been in continuous use for an extended period of time and/or if an awkward wrist posture is maintained. Additional stress is imposed on the worker's fingers, hand, wrist and arm by reason of the rapid motion of the piston in the tool cylinder.
As the pulling action of the tool on the lockbolt severs the pintail from the lockbolt-collar assembly, the resistance to the pulling force is suddenly eliminated, such that the tool is rapidly accelerated away from the lockbolt-collar assembly. The line of action of the jaw-anvil assembly is offset from the worker's hand and wrist so that a reaction torque can be generated against the worker's hand and wrist.